1. Field of the Invention
The field of the invention relates to telecommunication technologies, and in particular, to dynamic gateway selection processes for wireless telecommunications.
2. Description of the Prior Art
Legacy circuit switched telecommunication networks, such as the public switched telephone network (PSTN), typically provide very high reliability and quality of service. For instance, telephone calls can almost always be placed successfully. Once a call is established, the connection is clear and is rarely broken. One reason for these advantages is that the end points of circuit switched networks are fixed. A drawback is that fixed end points limit the flexibility of both carriers and customers.
In contrast, next generation packet networks are highly flexible as the end points are not fixed. For example, an end user can move from one access network to another using a mobile phone. In fact, a mobile phone in next generation networks need not only be conceived of as a wireless device. Rather, next generation phones can be plugged into to networks, such as through a broadband network connection. Next generation phones can also access networks through wireless mechanisms, such as WiFi hotspots. In these cases, and others, the end points change as the user roams across networks. A drawback to the flexible nature of next generation packet networks is that it is difficult to provide high quality service and reliability when the end points are constantly changing.
One example of the difficulty of providing reliable high quality service over packet networks involves the problem of gateway selection. Often times, a packet based service session includes an end point and a gateway. For instance, a standard voice over Internet Protocol (VoIP) voice call originates from an end point, such as a session initiation protocol (SIP) phone, and terminates to a destination on the PSTN. A gateway interfaces the originating packet network to the PSTN by interworking voice traffic between a packet format and a time division multiplexed (TDM) format.
During the call setup process, a soft switch selects the gateway to be used for the call based upon several methods, such as the open shortest path first (OSPF) method. The soft switch then caches the identity of the selected gateway with respect to the originating SIP phone. The next time the same SIP phone places a call to the PSTN, the same gateway is utilized. This is problematic because the quality of service provided on the previous call may not have been satisfactory. Furthermore, if the user has subsequently roamed to a new access point, the previous gateway may not even satisfy OSPF requirements. Thus, the current call could suffer from low quality of service due to an undesirable number of hops between the end device and the eventual gateway.